1. Field of the Invention
The present invention relates to a golf club.
2. Description of the Related Art
In an aspect of a development and sale of a golf club, a performance of a head or a shaft is evaluated. As an evaluating method, hitting is carried out through a tester, a swing robot or the like.
In the case in which the performances of the shafts are to be compared with each other, it is preferable to use the same type of heads to be attached to the shafts. By using the same type of heads, an influence of a difference in the head is lessened so that the performances of the shafts can be accurately compared with each other. For example, in the case in which a comparison test is carried out for three types of shafts, the same type of heads are attached to the three types of shafts respectively to execute the comparison test.
Even if the same type of heads are used, however, a variation in the performance is strictly present in the heads inevitably. In order to compare the performances of the shafts more accurately, it is preferable to sequentially attach the same head to each shaft, thereby carrying out the test.
The comparison test for the performance of the head is also the same as the foregoing. Even if the same type of shaft is attached to each head, a variation in the performance is strictly present in the shafts inevitably. In order to compare the performances of the heads with each other more accurately, it is preferable to sequentially attach the same shaft to each head, thereby carrying out the test.
In the case in which the performances of the head and the shaft are evaluated, accordingly, it is preferable that the head and the shaft should be attached and removed easily.
The easiness of the attachment and removal of the head and the shaft can be useful in various aspects. If the attachment and removal can easily be carried out, a golf player can easily attach the head and the shaft newly by himself (herself). For example, a golf player which cannot satisfy a performance of a purchased golf club can easily attach a head and a shaft newly by himself (herself). Moreover, the golf player himself (herself) can easily assemble an original golf club which is obtained by combining a favorite head with a favorite shaft. The golf player can purchase the favorite head and the favorite shaft and can assemble them by himself (herself). Furthermore, a shop for selling a golf club can select a combination of a head and a shaft which correspond to an aptitude for the golf player and can sell the golf club. A head and a shaft which can easily be attached and removed can cause the golf club to be readily custom-made.
Usually, the head and the shaft are bonded to each other with an adhesive. In order to separate the head and the shaft bonded to each other, it is necessary to pull the shaft from a shaft hole by a strong external force while heating a bonded portion at a high temperature to thermally decompose the adhesive. A labor, equipment and a time are required for the work. Moreover, there is also a possibility that the shaft or the head might be damaged in the heating or pull-out. Usually, the attachment and removal of the head and the shaft cannot be thus carried out easily.
On the other hand, US Patent Application No. US2006/0293115 A1 has disclosed a structure in which an attachment and removal of a head and a shaft can easily be carried out.